Biology Paper 2, WASSCE (PC), 2022

Question 3

(a)        List four components of a fertile soil and state two roles played by each of the
components.                                                                                                    [12 marks]
(b)        State four:
(i)         ways of conserving soil;                                                                      [4 marks]
(ii)        benefits of soil conservation.                                                              [4 marks]

Observation

Some candidates who attempted this question could not give the components of a fertile soil nor their roles in the soil. Many the components right lost marks to wrong spellings.

Some candidates could not give the required number of ways to conserve soil and the benefits of soil conservation.

The expected answers are:

(a)(i) Components of a Fertile Soil

- humus/organic matter
- water
- air
- mineral salt/organic matter
- living organisms
Any 4x1[4marks]
(ii) Roles played by Components

Soil Component

Two roles each

(i) Humus:

(ii)Water:

(iii) Air

(iv)Mineral Salt:

(v) Living Organisms

- enriches the soil with nutrients;
- serves as habitat for many soil microorganisms;
- prevent soil erosion/evaporation;
- hold water in the soil for plant use;
- improves soil structures/aeration.
Any 2x1[2marks]
- for transportation/photosynthesis/dissolution of
nutrients;
- improves soil structures;
- aids germination of seeds;
- aids turgidity of cells;
- moderates soil temperature.
Any 2x1[2marks]
- for plant growth/photosynthesis/respiration;
- promotes the germination of seed;
- aid in the weathering of rocks;
- needed in nutrient cycling e.g. carbon,
nitrogen cycle.
Any 2x1[2marks]
- provides support for plant;
- source of plant nutrients;
- holds water and air for living activities.
Any 2x1[2marks]

- improves soil structure/percolation/drainage;
- fixes nutrients into the soil e.g. bacteria;
- decompose organic material to form humus;
- stabilizes soil PH;
- improves the aeration of soil.
Any 2x1[2marks]

                        Any 4x1[4 marks]

(b)(i)    Ways of Conserving Soil
- practicing shifting cultivation/crop rotation;
- surface terracing;
- avoid bush burning;
- adding manure to soil;
- using cover crops;
- mulching;
- bush fallowing/planting of grass and trees/encourage afforestation.
Any 4x1[4marks]
(ii)     Benefits of Soil Conservation
- it ensures preservation of soil nutrients/soil fertility;
- it provides healthy habitat for soil;
- it provides raw- material for industries;
- it prevents desertification;
- it prevents soil erosion
- it encourages farming for food production